Interesting, just ordered these 2 days ago. Were they hard to take apart?

Is only one of the magnets angled/beveled or does the picture lie?

How thick is the felt on the bottom behind the ribbon?

What do you think of the quality of the original 15µ ribbon element?

It is very simple to take apart, but I do I would not recommend. You will almost certainly 100% ripped ribbon. As I did. I change ribbon for regular kitchen ALU foil. Measurement of the frequency response was the same as with original ribbon.

All the magnets (4) are angeled from both side. Angle is about 30-35 degres
The felt is about 2mm thick.

I think there is too much volume in the casing (behind the ribbon). When I will have more time, I will add some felt.

There is my project with JA8008 and NeoPro5i: (it is in SLOVENIAN language, but you can use google translate):

I like the attachment system of the ribbon. Should be easy to replace a ribbon yourself. Since this ribbon isn't even folded it should be a piece of cake to make your own out of kitchen foil. I have done ribbon replacements with kitchen alu foil in the past and they sounded exactly the same as the originals and all are still working.

The response curve does not look right since the tweeter and the mic were both lying on my kitched table during the test. Here's somewhat better measurement (with 500Hz/2nd. order high pass), although in quite echoing enviroment. All published data seems to correlate very well with the actual measured performance. Both ribbons also measure quite identical in all respects.

__________________
The path of least resistance goes through a triode, transformer and a horn.

I link this also here.
Fountek Neo Pro 5i Steps measurement at 90dB/1m:

I have been thinking to add more potting epoxy to the back chamber of the ribbon where the step-down transformer is to immerse the transformer totally in epoxy. I would also like to try some horn for the ribbon at some point, although it's in a small horn already.

__________________
The path of least resistance goes through a triode, transformer and a horn.